A recliner is a device installed in a seat, especially in a vehicle seat, to adjust a rotation angle of a seatback with respect to a seat cushion.
Especially, a round recliner, which is much related to the present invention, comprises a holder which is fixed to the seat, a sector gear which is fixed to the seatback and rotatably coupled to the holder, a plurality of lock gears which are accommodated in an inner space formed by the holder and the sector gear to slide in an overall circular direction according to a rotating operation of the cam thus performing locking and unlocking of the sector gear with respect to the holder.
Exemplary conventional inventions for such a round recliner include Korean Patent Registration No. 513576 “ROUND RECLINER FOR VEHICLE” (registered on Sep. 1, 2005), Korean Patent Registration No. 575397 “RECLINER FOR VEHICLE” (registered on Apr. 25, 2006), Korean Patent Registration No. 575398 “RECLINER FOR VEHICLE” (registered on Apr. 25, 2006) and etc.
FIG. 1 is a schematic view of a recliner which shows typical characteristics of the conventional inventions.
In FIG. 1, a lock gear 500 slides along a lock gear guide of a holder 300 so that teeth 510 of an outer round surface of the lock gear 500 interlock with inner teeth (not shown) of a sector gear (not shown).
According to such a conventional round recliner, a lock gear guide 320 and the lock gear 500 have an operating clearance to a predetermined amount for a smooth sliding movement therebetween.
However, due to existence of such operating clearance, rotational clearance is generated as much as the operating clearance between the lock gear 500 and the lock gear guide 320 even when the sector gear (not shown) is locked with respect to the holder 300, so that rattling of the seatback is generated.
Also, there are three lock gears 500 for locking the sector gear (not shown) according to the conventional round recliner as described above.
However, according to experiments, substantially only one lock gear 500 exerts locking force in most cases when there is an outer rotational impact on the sector gear, which may cause safety problem that the sector gear in a locking state can rotate freely due to deformation of teeth 510 if an outer impact of a significant amount is exerted.